Working zinc alloys



, Patented Aug. 15, 1939 UNITED STATES PATENT OFFICE WORKING ZINC ALLOYSApplication September 23, 1937, Serial No. 165,322 In Germany June 2,1937 4 Claims.

This invention relates to improvements in forming alloy metal objectsand particularly to working zinc alloys containing from 10 to 20%aluminum to produce'an alloy object without im- 6 pairing the mechanicalproperties of the alloys.

Zinc generally is rolled at temperatures below 200 C. because itsrollability is decreased at higher temperatures. The presence of othersubstances in the zinc generally decreases the rollability so that therolling temperature must be increased in the case of zinc alloys.However, in practice, temperatures of 270 C. are not exceeded becausethis tends to bring about deterioration in the mechanical properties ofthe rolled alloys. Moreover, the temperature cannot be decreased below180 C. on account of the high roll pressures then requisite. (A.Burkhardt, Technologie der Zinklegierungen, Berlin 1937, page 192.)

We have found, however, that aluminum-bearing zinc base alloyscontaining from 10 to 20% of aluminum can readily be rolled andotherwise worked at temperatures between 270 and 380 C.. and preferablyat a temperature of about 340 C. Although the addition of aluminumgenerally decreases the rollability of zinc so far that at 25 mediumtemperatures only slight decreases in thickness are possible at eachpass, it was unexpeetedly found that at temperatures about 270 C. themalleability of zinc-base alloys containing 10 to 20% of aluminumincreased so suddenly and the work of deformation decreased so rapidlythat in this range hot working is possible with heavy reductions at eachpass. The mechanical properties of the resuting zinc alloy objects arenot impaired by this method of treatment, but 3 instead are generallyimproved. Thus we have discovered that the malleability of an alloyconsisting of 10 to 15% aluminum, 1.5 to 4% copper and .01 to .04%magnesium, the balance of the alloy being zinc having a purity of atleast 99.98% (as described in co-pending United States application No.159,711, filed August 18th, 1937, by Herbert Winter, and subsequentlyissued as United States Patent No. 2,102,869, on December 21, 1937)increases suddenly at temperatures above 270 C. and retains thisincreased mallea- -bility to. a temperature of about 380 C. At atemperature of 340 C. the malleability of this alloy is optimum.

Our invention, therefore, contemplates the improvement in themanufacture of zinc base objects which comprises working at atemperature ranging from 270 C. to 380 C., and preferably at 340 C. azinc-base alloy containing from 10 55 to 20% aluminum, and moreparticularly an alloy consisting of 10 to 15% aluminum, 1.5 to 4%copper, .01 to .04 magnesium, the balance of the alloy being zinc havinga purity of at least 99.98%. When such alloys are thus worked, there isno deterioration in their mechanical properties. On the contrary, theresulting metal objects possess high tensile and impact strengths, 6improved machinability and high resistance to corrosion.

The curves A and B in the accompanying single figure illustrate thesudden increase in malleability of aluminum-bearing zinc base alloysthat we have discovered. Two alloys A and B were subjected underconstant load to difierent temperatures. In the figure the ordinatesshow the change of form suffered by the test rods under a compression of7.5 kilograms per square millimeter. The change in form was measured inper cent decrease in the height of the pieces under compression. Theabscissae in the figure show the temperature of deformation in degreesCentigrade. The compositions of the alloys investigated were as follows:

We claim:

1. In the manufacture of zinc alloy objects, the improvement whichcomprises working at a temperature ranging from 270 to 380 C. analuminum-bearing zinc base alloy containing from 10 to 20% aluminum.

2. In the manufacture of zinc alloy objects, the improvement whichcomprises working at a temperature of about 340 C. an aluminum-bear ingzinc base alloy containing from 10' to 20% aluminum.

3. In the manufacture of zinc alloy objects, the.improvement whichcomprises working .at a temperature ranging from 270 to 380 C. analloyconsisting of 10 to 15% aluminum, 1.5 to 4% copper and 0.01 to0.04% magnesium, the balance of the alloy being zinc having-a purity ofat least 99.98%.

4. In the manufacture of a zinc alloy object, the improvement whichcomprises working at a temperature of about 340 C. an alloy consistingof 10 to 15% aluminumflfi to 4% copper, and 0.01 to 0.04 magnesium, thebalance of the alloy being zinc having a purity of at least 99.98%.

HERBERT WINTER. WOLFGANG FAHRENHORBT.

ERICH SCHIJID.

